If we are ever to know with any certainty that crisis lines are effective in reducing deaths from suicide, or in managing distress levels in individuals before they are suicidal, three essential questions must be addressed: 1. Of the entire population of potential callers to a crisis line, what are the characteristics of individuals who cll a crisis line? 2. What are the key behavioral characteristics of responders that moderate individual characteristics of callers, resulting in acceptance of a referral given from a responder to the caller? 3. Is there an impact on important outcomes: death from suicide, suicide attempts and reattempts, hospitalization for suicidal behaviors, engagement in an ongoing safety planning process, and overall reductions in psycho-social distress? PUBLIC HEALTH RELEVANCE: We view a study of the Department of Veterans Affairs' (VA's) 24/7 Crisis Line (formerly called the VA Suicide Hotline) as significant since suicide prevention crisis lines continue to be an intervention of great interest, while still defying reaching a high standard of proven effectiveness. Due to the very nature of community crisis lines, by virtue of their anonymity, it is difficult to answer three questions that must be addressed if we are ever to know with any certainty that crisis lines are effective in reducing deaths from suicide, or in managing distress levels in individuals before they are suicidal. These questions underscore the significance of this application because of our distinct ability to address issues that cannot be done in any other crisis line setting: 1. Of the entire population of potential callers to a crisisline, what are the characteristics of individuals who call a crisis line? 2. What are the key behavioral characteristics of responders that moderate individual characteristics of callers, resulting in acceptance of a referral given from a responder to the caller? 3. Is there an impact on important outcomes: death from suicide, suicide attempts and reattempts, hospitalization for suicidal behaviors, engagement in an ongoing safety planning process, and overall reductions in psycho-social distress? We recognize that considerable advances have been made in addressing Questions 1 and 2; indeed, Dr. Madelyn Gould who is a Co-Investigator on this study has been a leader, with others, in the field of examining the utility of suicide crisis lines But a critical difference between the national network of suicide crisis lines across the United States (National Suicide Prevention Lifeline, or NSPL) and VA's Crisis Line is that the VA's Crisis Line has the enhanced ability to study characteristics of callers and responders, the capacity to provide nation-wide services through immediate referral and follow-up care, and the critical capacity to identify outcomes in callers to the Crisis Line. Through the use of some new, innovative methods, including causal modeling, we have developed a study that we strongly believe has the potential to have a high impact on delivery of care through suicide crisis lines. I summary: This may not be the perfect study of the effectiveness of a suicide crisis line, but it overcomes many of the limitations inherent to studies of community crisis lines.